Playing to an audience: The social environment influences aggression and victory displays
A new article in Biology Letters by Lauren Fitzsimmons and Susan Bertram
In nature, many animals fight for dominance, territories, and mates, and fights often occur when others are watching (Figure 1). For example, eavesdropping fish are more likely to initiate fights with a loser than a winner, imposing an immediate cost to the loser. Fighters also sometimes change their behaviour when they know they are being watched.
Humans do this regularly: consider the classic victory dance following a touchdown in a football game (Figure 2). Fish do this too: male fish have been shown to change their female preference in the presence of a potential competitor.
We conducted the first investigation of how audiences affect fighting and victory displays in an invertebrate, the spring field cricket (Gryllus veletis; Figure 3). Male field crickets frequently engage in fights over resources (see video here).
Winning a fight increases a male’s mating success through dominance which provides access to mate attraction territories, and because females usually prefer to mate with dominant males. Cricket fight winners often advertise their success using victory displays of aggressive songs and body jerks (shown after the fight in the video linked above). Because cricket densities can be high in field crickets, and mate attraction and fights occur in close proximity, many fights are likely to occur with female and male audiences nearby.
We investigated aggression and victory display behaviour in both field-captured and laboratory-reared crickets to explore the effect of rearing environment on these behaviours. We predicted that males with social experience would change their behaviour depending on the social context, whereas inexperienced lab-reared males would be less likely to respond to the presence of an audience. We found that the type of audience and the rearing environment (field or lab) were important predictors of how males behaved during and after fights. Field-captured winners were more aggressive than laboratory-reared winners in the presence of an audience (Figure 4).
Field-captured winners produced more victory displays in the presence of a male audience compared to no audience, whereas the victory display behaviour of lab-reared males was similar across audiences and highly variable among males within audience conditions (Figure 5). Our results suggest that field-captured winners, in particular, dynamically adjust their fighting behaviour to potentially gain a reproductive benefit via female eavesdropping and may deter future aggression from rivals by advertising their aggressiveness and victories.
Female mating decisions and male fighting decisions may be influenced by information communicated during contests, and females may represent a valuable resource for the winner, providing advantages to elevated aggression by winners during fights. Indeed, we found that contest winners elevate aggression in the presence of a female audience compared to no audience. Contest winners may be selected to be more aggressive and give more victory displays with male audiences because these displays reduce the likelihood of future contests; victory displays may also advertise additional energy that could be used against potential rivals. It is unknown whether cricket audiences gain information through eavesdropping, but our results suggest potential payoffs for both victorious males and eavesdroppers.
The relative lack of response to audience treatments for lab-reared males may reflect a lack of social experience. Our findings suggest that experiments on naive lab-reared individuals may not accurately reflect the behaviour of wild animals in nature, and add to evidence that social experience is important in shaping the development of dynamic behaviours. Field-captured males may be better able to adjust their dynamic behaviours to different social environments after experiencing both their own aggressive encounters and observing interactions between other males.
Our study provides the first evidence that invertebrates modify their contest behaviour in the presence of an audience. The ability to perceive the presence and sex of an audience and adjust behaviour accordingly is thus not restricted to vertebrates and may be more common across animals than previously recognized. Our study also provides the first evidence of an audience effect on victory display behaviour, and highlights the importance of the social environment in shaping animal behaviour.
- Cricket winners show off (nature.com)
- Top News: Crickets Act Differently When Others Are Watching (news.nationalgeographic.com)
- Crickets talk trash, dance and brag, study finds (cbc.ca)
- Crickets Act Differently When Others Are Watching (everythinganimals.net)
- Everybody loves an audience – even crickets (nation.com.pk)
- Just like Brad Marchand, crickets chirp and strut after combat (with video) (blogs.windsorstar.com)
- Audience effect in Siamese fighting fish (oxfordjournals.org)
- Social environment influences sexual behaviour in crickets (sciencedirect.com)